21012210997 has 2 divisors, whose sum is σ = 21012210998. Its totient is φ = 21012210996.

The previous prime is 21012210977. The next prime is 21012211007. The reversal of 21012210997 is 79901221012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18703024081 + 2309186916 = 136759^2 + 48054^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21012210997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012210977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506105498 + 10506105499.

It is an arithmetic number, because the mean of its divisors is an integer number (10506105499).

Almost surely, 2^21012210997 is an apocalyptic number.

It is an amenable number.

21012210997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012210997 is an equidigital number, since it uses as much as digits as its factorization.

21012210997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 34.

The spelling of 21012210997 in words is "twenty-one billion, twelve million, two hundred ten thousand, nine hundred ninety-seven".